Metals, glass, and plastics are common fabrication materials used in many commercial and industrial applications. The surfaces of these materials have a wide range of finishes. The finish of these surfaces defines the texture of the material, which ranges from a highly polished surface to a visually and/or tactilely rough surface. Further, the aforementioned materials are non-tacky (i.e. non adhesive) and require the use of an adhesive to adhere one surface of the material to the other.
Inspired by the ability of the gecko to adhere to most surfaces at any angle, attempts at developing dry adhesives mimicking the spatula tipped setae on the gecko feet pads have been carried out at many institutions. Geckos can instantaneously and repeatedly attach and detach their fibrillar feet pads to a wide range of surfaces without leaving residues. Typical approaches to produce such a dry adhesive have consisted in designing and fabricating synthetic gecko setae. However, the gecko's setae have a complicated branched structure. A single gecko may have two millions setae on its feet. Each seta may branch into hundreds of spatula-shape tips. These spatula-shape tips are about 200 nanometers in diameter. It is believed that the adhesive force of the gecko feet pads results from the cumulative effect of van der Waals forces between the millions of setae on the feet pads in intimate contact with the surface the gecko is climbing on.
On another subject, inkjet printers have become ubiquitous and an indispensable tool in homes and small offices. Inexpensive inkjet printers typically employ water-based inks to print on uncoated or coated paper. The quality of images printed on coated paper with an inkjet printer has exceeded the visual threshold and can thus compete with photographic silver halide processes.
However, there are a number of problems and/or disadvantages associated water-based inks. A first problem is that these inks are water soluble. Therefore, the images printed with such inks may not be waterfast. A small drop of water can cause severe smearing of the information on the printed image. The smeared image may often be irrecoverably damaged and/or information on the image may be permanently lost.
Another problem associated with images printed with inkjet printers is archival. Images printed with inkjet printers have a limited lifetime due to low lightfastness of the inks involved. Dye based inks tend to fade in a relatively short time. Further, each color has a tendency to fade at a different rate leading to a change in the image color balance.
In the prior art, waterfastness and/or lightfastness have been improved by using solvent based inks. Such inks are not water soluble, and the images they produce thus tend to be waterfast and lightfast. However, the main components in solvent ink are volatile organic compounds (VOC). These VOCs make these inks less environmentally friendly.
A more environmentally friendly solution is to laminate a protective film over the printed image. Laminating films are available as thermally activated film and/or pressure sensitive, heatless film. Thermally activated films typically contain a heat-activated adhesive and are applied using a heated roll laminator to irreversibly bond the film to the substrate. In such hot melt lamination processes, the thickness of the laminating film is limited by heat transfer constraints. This is because polymers used to make these films typically are thermal insulators that do not conduct heat very well. Thus the thickness of the film will be limited as only films that are thin enough to allow sufficient heat transfer to melt the adhesive layer can be used. Pressure sensitive film contains a pressure sensitive adhesive (glue) that is protected with a backing film that does not adhere to the glue. When the backing film is removed, the pressure sensitive adhesive layer is applied with a cold roll laminator to irreversibly bond to the film to the substrate via the glue.
A disadvantage of such laminating films is that complex laminating equipments is typically required to apply the required heat and/or pressure in order to adhere the laminating film to the printed image. Further, the bond between the printed image and laminating film is generally permanent and thus the laminating film may not be readjusted or removed once the lamination process is completed.
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.